" SCP-XXXX is to be contained in a 3m x 3m x 4m concrete containment unit within [REDACTED]."

I'm not sure having a redacted bit of information in the Containment Procedures is a great idea. If I'm not mistaken the idea behind having these procedures is so that an average employee can check the file in case of an emergency happening. Imagine if the SCP were to escape, and for a task force to finally capture it, only for them to not know where exactly to take it. I think having the name of the place it is kept is important for that reason.

Am I correct to assume this is a reference to Sonic the Hedgehog? If it isn't feel free to ignore this next part, but I think there is a bit of a dilemma when it comes to writing a bit of short fiction based on a character like this. For one, if people don't know the reference, the point of the SCP isn't exactly obvious. If I hadn't heard of Sonic before, all I could really take away from this SCP is that it is a spiky monster that says weird stuff sometimes. The fact that it is blue or has references to running fast wouldn't make an impression, and would seem more like fluff for fluff's sake. Try to find something that would really appeal to people in general. That being said, taking inspiration from something is great, but instead of looking for aesthetics in your inspiration, try boiling whatever it is you are inspired by into its base elements and seeing exactly what about that attracts you. If you like Sonic, it probably isn't because he is a blue hedgehog. It might be because you like his attitude, or the gameplay of those videogames, or his relationships with other characters. Those are the sorts of things you need to consider (though obviously gameplay isn't really translatable into prose easily).

"SCP-XXXX's body structure seems have to been altered by seemingly unnatural means with its skin bearing stretch marks around its joints."

You might consider either elaborating more so on how it had been altered or deleting the sentence, as it isn't doing anything for the post. Stretch marks aren't exactly unnatural for anyone who has gained or lost weight or muscle. Also, I think we can assume that any sort of transformation this monster has gone through is unnatural, so saying that isn't really necessary.

"A Pantone orange (#FF5800) layer must be maintained around the containment unit to easily spot leakages originating from SCP-XXXX."

I actually really like that you are adding details like the color of the containment chamber, but you should consider steps to actually removing the leakage as well. Is there a vacuum device that's going to suck it up? Is the SCP going to be removed so janitors can clean? If so, where will the SCP be held during cleaning?

"will begin to excrete the corrosive liquid at a accelerated"
That needs to be 'an accelerated rate'.

"SCP-XXXX can vocalize a small number of words1 which has been vocalized at a volume of between 70 and 140 decibels."

Consider tightening up some of your sentences like this one. If you already have the word vocalize in your sentence, you don't need that word again. Take a look at this version of the same sentence. "SCP-XXXX can vocalize a small number of words1 at a volume of between 70 and 140 decibels." By tightening up things like that, the prose will read much more fluidly.

As a courtesy to our readers on mobile devices, please collapse long posts. ~Zyn

My suggestion overall for this SCP is to either rework it so that there is more to it than "evil Sonic", or for you to cut those aspects out of it. Consider a theme. As fun as it might be to think of your favorite characters as monsters, without a theme, it is difficult to leave a lasting impression. If you are completely married to the idea of bringing evil videogame monsters into your SCP, consider starting over with a mindset of bringing the themes and execution of that property instead of the aesthetic. That way people who have no idea who Sonic is have something to latch onto and enjoy about your SCP. Can you tell me what exactly about Sonic attracts you to him, and why you think he is a good fit for SCPs? Maybe by answering that we could come up with something a bit punchier for your next try.

Colonel_Bass The feedback you are providing, while correct, is little to none. The little number of things you have pointed out harms an author more than helps, which is due to two reasons.
One is that staff and other critters will search for drafts with only one response, and they may be able to give a more in-detail critique.
The second is that the author may see the little amount of things you have brought up and think it might be main site ready when, it might not be, thus it gets downvoted in expectedly.